Collaborative Research: Testing for large scale Hawaiian arch volcanism and associated magma sources

合作研究：测试大规模夏威夷拱形火山活动和相关岩浆源

• 批准号: 1936453
• 负责人: Aaron Pietruszka
• 金额: $ 3.8万
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-05-01 至 2023-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1936453&HistoricalAwards=false
• 关键词: Collaborative; Research; Testing; large; scale

When large volcanic structures such as the Hawaiian islands and seamounts are constructed on the seafloor their mass can cause large flexural bulges in the seafloor surrounding them. In some places, unique volcanic features have been observed along the fractures that form in association with these flexural bulges. The volcanic processes that form these features are not well studied or well understood. In particular, the depth and underlying properties of the magma that feed these submarine volcanic events are heavily debated. In the fall of 2018, a seagoing expedition sampled several volcanic seamounts that formed along the flexural bulge associated with an ancient section of the Hawaiian seamount chain. The flat tops of some of the seamounts that were sampled indicate they were once large enough to breach the surface of the ocean. Through radiometric dating and geochemical analyses of the lava flow samples, this project will unravel the underlying forces that generated these enigmatic seamounts. The project supports the training of an early career scientist and two graduate students.Arch volcanism is currently an underappreciated and poorly understood magmatic process. Moreover, available work on the ages and compositions of Hawaiian Arch volcanism has not yet led to a consensus of the type of source material involved, the potential dynamics of the process, or even the potential scale. A recent sampling expedition targeted and sampled a set of enigmatic seamounts located exactly on (an older part of) the Hawaiian Arch. Their size and location adjacent to one of the largest Hawaiian volcanic complexes (Gardner Pinnacles) hints at the potential relationship between flexural amplitude and arch melt productivity, with lavas reaching unexpected volumes. This project will conduct 40Ar/39Ar age determinations, major and trace element concentrations and Sr-Nd-Pb isotopic analyses on basaltic rock samples recovered from two previously unexplored seamounts chains. These chains are not part of the primary Hawaiian plume track but reside on the flexural bulge, north of the massive Gardner Seamount within the Papahanaumokuakea Marine National Monument. Recent mapping revealed two guyots along the chains, indicating both features were large enough to breach the sea surface. The overarching goal of this project is to determine the volcanic processes that produced such large volcanic features so far from the track of the main plume. The hypothesizes to be tested are 1) The enigmatic seamount clusters north of Gardner Pinnacles were formed by processes associated with arch volcanism, 2) Arch volcanism can produce massive seamounts, and 3) The geochemical affinities of lavas from these seamounts are similar to rocks formed by rejuvenated volcanism. This project will test these hypotheses with a new suite of petrological, geochemical and geochronological constraints. If the results show that arch volcanism produced these seamounts, the results would imply that arch volcanism can produce features much larger than previously thought. More broadly, this work will speak directly to the discussion of shallow versus deep controls for hot spot volcanism and the types and locations of source materials.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

当夏威夷群岛和海山等大型火山结构建在海底时，它们的质量可能会导致周围海底出现大的弯曲隆起。在一些地方，沿着与这些弯曲凸起相关的裂缝观察到了独特的火山特征。形成这些特征的火山过程尚未得到充分研究或充分理解。特别是，为这些海底火山事件提供营养的岩浆的深度和潜在特性引起了激烈的争论。 2018 年秋天，一支航海探险队对几座火山海山进行了采样，这些火山海山是沿着与夏威夷海山链的古代部分相关的弯曲隆起形成的。取样的一些海山的平顶表明它们曾经大到足以冲破海洋表面。通过对熔岩流样本进行放射性测年和地球化学分析，该项目将揭示产生这些神秘海山的潜在力量。该项目支持培训一名早期职业科学家和两名研究生。拱火山作用目前是一种未被充分认识和了解的岩浆过程。此外，关于夏威夷拱门火山活动的年龄和成分的现有工作尚未就所涉及的源物质类型、过程的潜在动态甚至潜在规模达成共识。最近的一次采样考察针对恰好位于夏威夷拱门（较旧部分）的一组神秘海山进行了采样。它们的大小和位置毗邻夏威夷最大的火山群之一（加德纳尖峰石阵），暗示了弯曲幅度和拱形融化生产力之间的潜在关系，熔岩达到了意想不到的体积。该项目将对从两个先前未勘探的海山链中回收的玄武岩样品进行 40Ar/39Ar 年龄测定、主量和微量元素浓度以及 Sr-Nd-Pb 同位素分析。这些链不是夏威夷主要羽流轨迹的一部分，而是位于帕帕哈瑙莫夸基亚海洋国家保护区内巨大的加德纳海山以北的弯曲隆起处。最近的测绘显示，沿着链条发现了两个居奥特，这表明这两个特征都足够大，足以突破海面。该项目的总体目标是确定产生远离主羽流轨迹的如此大火山特征的火山过程。要测试的假设是 1) 加德纳尖峰石阵以北的神秘海山群是由与拱形火山作用相关的过程形成的，2) 拱形火山作用可以产生巨大的海山，3) 这些海山熔岩的地球化学亲和力与形成的岩石相似通过复兴的火山作用。该项目将通过一套新的岩石学、地球化学和地质年代学约束来测试这些假设。如果结果表明拱火山活动产生了这些海山，那么结果将意味着拱火山活动可以产生比之前认为的大得多的特征。更广泛地说，这项工作将直接讨论热点火山活动的浅层与深层控制以及源材料的类型和位置。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力优点和技术进行评估，被认为值得支持。更广泛的影响审查标准。